The subject matter disclosed herein generally relates to airfoil platforms used in gas turbine engines and, more particularly, to airfoil platforms having bowed sidewalls.
Gas turbine engines generally include a fan section, a compressor second, a combustor section, and turbine sections positioned along a centerline referred to as an “axis of rotation.” The fan, compressor, and combustor sections add work to air (also referred to as “core gas”) flowing through the engine. The turbine extracts work from the core gas flow to drive the fan and compressor sections. The fan, compressor, and turbine sections each include a series of stator and rotor assemblies. The stator assemblies, which do not rotate (but may have variable pitch vanes), increase the efficiency of the engine by guiding core gas flow into or out of the rotor assemblies.
The fan section includes a rotor assembly and a stator assembly. The rotor assembly of the fan includes a rotor disk and a plurality of outwardly extending rotor blades. Each rotor blade includes an airfoil portion, a dove-tailed root portion, and a platform. The airfoil portion extends through the flow path and interacts with the working medium gases to transfer energy between the rotor blade and working medium gases. The dove-tailed root portion engages attachment means of the rotor disk. The platform typically extends circumferentially from the rotor blade to a platform of an adjacent rotor blade. The platform is disposed radially between the airfoil portion and the root portion. The stator assembly includes a fan case, which circumscribes the rotor assembly in close proximity to the tips of the rotor blades.
To reduce the size and cost of the rotor blades, the platform size may be reduced and a separate fan blade platform may be attached to the rotor disk. To accommodate the separate fan blade platforms, outwardly extending tabs may be forged onto the rotor disk to enable attachment of the platforms. Fan platforms having either straight or more than one straight feature joined by blend radii may create high inter-laminar stresses due to high tensile loading through the fillets and a thin, fragile geometry may be needed for internal mold tools.